The present invention relates to systems and methods for extracting contaminants from rotating electrical devices, and more particularly to systems and methods for vacuum extracting brush contaminants from synchronous generators.
Rotating electrical devices such as generators and motors often utilize wearable, conductive components referred to as brushes to transfer electricity from rotating parts to stationary parts. One example of such a rotating electrical device is the type of synchronous generator used in the power generation industry.
In the power generation industry, synchronous generators are used to convert rotary mechanical energy supplied by a power source such as a steam or combustion turbine or a nuclear reactor into electrical energy. Such synchronous generators generally comprise two main sections: a rotor and a stator. The rotor is typically wound with conductors called field windings. The field windings are made up of straight sections that run the length of the rotor and end sections that connect the straight sections into one long conductor. The stator is also typically wound with conductors called stator windings.
When rotary mechanical energy causes the rotor of the synchronous generator to spin, the field windings turn inside of the stator windings. If the field windings are supplied with an excitation current, the field windings produce a magnetic flux that induces an electric current in the stator windings as they turn inside of the stator windings.
One conventional method for supplying excitation current to field windings is called static excitation. In static excitation systems, a current collection system is used to transfer excitation current from an exciter to the field windings on the spinning rotor. The current collection system includes a set collector rings and a set of corresponding brushes. The collector rings are mounted to the circumference of the rotor and are electrically connected to the field windings. The brushes, which are generally made of a wearable, conductive material such as carbon or graphite, are held in sliding contact with corresponding collector rings to form a sliding, electrical connection to the field windings on the spinning rotor.
A significant disadvantage of such static excitation systems is that the brushes they utilize wear over time as they slide against the collector rings and must periodically be replaced. In addition, as the brushes wear, they produce a conductive dust as a contaminant byproduct, which if permitted to accumulate may cause electrical shorts or arcing. Such electrical shorts or arcing can cause severe damage to electrical devices.
In the power generation industry, in order to prevent damage from electrical shorts or arcing, equipment operators are required to frequently inspect and clean the current collection systems of generators. This daily inspection and cleaning is tedious and time consuming. It also exposes equipment operators to dangerous high-voltage conditions in and around the current collection system.
Methods and systems consistent with the present invention provide a vacuum extraction system that automatically extracts contamination produced by wearable brushes or other wearable components in rotating electrical devices. The vacuum extraction system substantially reduces the frequency with which inspections and cleanings are required, which reduces the operating costs of the rotating electrical devices. By reducing the frequency with which inspection and cleanings are required, the vacuum extraction system also reduces the frequency with which operators are exposed to dangerous high-voltage conditions. In addition, the vacuum extraction system produces increased air flow in and around the current collection system, which cools and extends the life of the components of the current collection system.
Systems and methods consistent with the present invention provide a dust extraction system for extracting contamination from rotating electrical devices. Consistent with one embodiment of the present invention, a vacuum extraction system is provided for extracting dust from a current collection system. The vacuum extraction system comprises a brush holder assembly comprising a brush holder for holding a brush in sliding contact with a collector ring, a vacuum passage for extracting air and contaminants from said current collection system, a dust capture media in vacuum connection with said vacuum passage for capturing contaminants from said air, and a vacuum source in vacuum connection with said dust capture media for supplying vacuum to said vacuum extraction system. Consistent with another embodiment of the present invention, a method of extracting contaminants is provided from a current collection system utilizing a brush in sliding contact with a collector ring. The method comprises the steps of providing a vacuum passage proximate the contact area between said brush and said collector ring, connecting said vacuum passage to a dust capture media via a vacuum connection, connecting said dust capture media to a vacuum source for providing a vacuum at said vacuum passage, and extracting said contaminants away from said contact area via said vacuum into said dust capture media.
Consistent with another embodiment of the present invention a synchronous generator utilizing an excitation current from an exciter is provided. The generator comprises a stator having stator windings; a rotor rotatable within said stator and having field windings for inducing a current in said stator windings; a current collection system for transferring said excitation current from said exciter to said field windings; a vacuum extraction system for extracting dust from said current collection system, said vacuum extraction system comprising a brush holder assembly that comprises a brush holder for holding a brush in sliding, contact with a collector ring, a vacuum passage for extracting air and contaminants from said current collection system, a dust capture media in vacuum connection with said vacuum passage for capturing contaminants from said air, and a vacuum source in vacuum connection with said dust capture media for supplying vacuum to said vacuum extraction system.